Abstract
Active control over the shape, composition, and crystalline habit of nanocrystals has long been a goal. Various methods have been shown to enable postsynthesis modification of nanoparticles, including the use of the Kirkendall effect, galvanic replacement, and cation or anion exchange, all taking advantage of enhanced solid-state diffusion on the nanoscale. In all these processes, however, alteration of the nanoparticles requires introduction of new precursor materials. Here we show that for cesium lead halide perovskite nanoparticles, a reversible structural and compositional change can be induced at room temperature solely by modification of the ligand shell composition in solution. The reversible transformation of cubic CsPbX3 nanocrystals to rhombohedral Cs4PbX6 nanocrystals is achieved by controlling the ratio of oleylamine to oleic acid capping molecules. High-resolution transmission electron microscopy investigation of Cs4PbX6 reveals the growth habit of the rhombohedral crystal structure is composed of a zero-dimensional layered network of isolated PbX6 octahedra separated by Cs cation planes. The reversible transformation between the two phases involves an exfoliation and recrystalliztion process. This scheme enables fabrication of high-purity monodispersed Cs4PbX6 nanoparticles with controlled sizes. Also, depending on the final size of the Cs4PbX6 nanoparticles as tuned by the reaction time, the back reaction yields CsPbX3 nanoplatelets with a controlled thickness. In addition, detailed surface analysis provides insight into the impact of the ligand composition on surface stabilization that, consecutively, acts as the driving force in phase and shape transformations in cesium lead halide perovskites.
| Original language | English |
|---|---|
| Pages (from-to) | 84-93 |
| Number of pages | 10 |
| Journal | Chemistry of Materials |
| Volume | 30 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 9 Jan 2018 |
Funding
This research was supported by a grant from the Israel Science Foundation (Grant 2012\224330*) and by the Crown Center of Photonics and the ICORE: the Israeli Excellence Center “Circle of Light”. The support of the Gerhardt M. J. Schmidt Minerva Center and the Irving and Cerna Moskowitz Center for Nano and Bionano Imaging and at the Ernst-Ruska Centre (Jülich, Germany) is also gratefully acknowledged. Author Contributions T.U. synthesized the nanocrystals and performed XRD and TEM measurements. L.H. performed HRTEM measurements and analysis. T.U., A.T., and M.K. performed the optical characterization. M.M., I.P., and O.Y. performed Raman scattering measurements and analysis. H.C. performed XPS measurements and analysis. L.A. performed solution NMR measurements. T.W. performed ssNMR measurements. M.L., T.W., and L.A. performed analysis of NMR data. M.K. and D.O. conceived and supervised the project. The manuscript was jointly written by all authors.